1. Field of the Invention
The present invention relates to new caffeoyl-CoA 3-O-methyltransferase genes (called CCoAMT genes below) isolated from plants and to their use for the transformation of vectors, host organisms and plants and for the generation of plants which have an increased resistance to pests.
2. Description of the Related Art
The enzyme caffeoyl-CoA 3-O-methyltransferase, called CCoAMT below, catalyses the methylation of caffeoyl-CoA in a biosynthesis route, which has only recently been described, which leads from trans-4-coumaroyl-CoA to trans-feruloyl-CoA (Matern, U., and Kneusel, R. E. 1988, Phytoparasitica 16:153-170; Kneusel, R. E., Matern, U., and Nicolay, K. 1989, Arch. Biochem. Biophys. 269:455 to 462; and Pakusch, A. -E., Kneusel, R. E., and Matern, U., 1989, Arch. Biochem. Biophys. 271:488 to 494).
Under fungal attack, plants reinforce their cell wall very rapidly by incorporation of cinnamic acids, followed by cross-linking thereof to give polymeric structures or build-up of lignin. Under these conditions, feruloyl-CoA is the preferred acyl donor both for the esterification of cell wall polysaccharides and for lignification (reduction to coniferyl alcohol). The speed and extent of the change in the cell wall essentially determine the course of the infection and the fate of the plants, "hypersensitive reaction" characterising complete resistance of the plants, associated with a particularly severe and rapid change in the cell wall and the death of the cells directly affected. This hypersensitive reaction is also observed in the resistance reaction of plants to virus infections. It has only recently been discovered that feruloyl-CoA is not formed in vivo in all cases by activation of ferulic acid, but is also formed by reaction of coumaroyl-CoA. The caffeoyl-CoA-specific methyl-transferase which participates in this reaction has scarcely any homology with previously known enzymes (Pakusch, A. -E., Matern, U., and Schiltz, E., 1991, Plant Physiol. 95:137 to 143), is taxonomically widespread in plants and can be induced therein by, for example, fungal attack.
A large proportion of the world harvest of crop plants is constantly destroyed by pests (in 1967 the loss of potential harvest was 35%; compare Chemistry of Pesticides, published by K. H. Buchel, John Wiley & Sons, New York, 1983, page 6). There is therefore an urgent need to research and utilise all possibilities which are capable of reducing or preventing attack of crop plants by pests.